Infrared Band Pass Filter

ABSTRACT

The present disclosure relates to an infrared band pass filter, which comprises a first multilayer film. The first multilayer film including a plurality of Si:NH layers and a low refraction index layer. The plurality of low refraction index layers are stacked with Si:NH layers alternatively; wherein the difference between the refraction index of Si:NH layer and the refraction index of the low refraction index layer is greater than 0.5. The infrared band pass filter has a pass band in a wavelength range of 800 nm and 1100 nm, and when the incident angle is changed from 0 degrees to 30 degrees, the center wavelength of the pass band is shifted less than 12 nm, and the infrared band pass filter of the present disclosure can be used to enhance the 3D image resolution when applied to a 3D imaging system.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Chinese Patent Application Serial Number 201810921532.7, filed on Aug. 14, 2018, the full disclosure of which is incorporated herein by reference.

BACKGROUND Technical Field

The present disclosure relates to the technical field of optical filtering, and more particularly to an infrared band pass filter.

Related Art

The existing infrared band pass filter comprises an optical substrate having a multilayer film formed on one surface of the optical substrate, and a multilayer anti-refraction layer formed on the other surface thereof. The multilayer film is formed by alternately depositing a plurality of high refractive index layers and a plurality of low refractive index layers. The material of the high refraction index layer is selected from the group consisting of Ti₃O₅, Ta₂O₅, ZrO₂, Nb₂O₅ and TiO₂ and the material of the low refraction index layer is selected from one of the MgF₂ and SiO₂.

The infrared band pass filter has a pass band in the wavelength range between 800 nm and 1100 nm. When the incident angle is changed from 0 degrees to 30 degrees, the center wavelength of the pass band is shifted between 31 nm and 34 nm. The center wavelength of the pass band is greatly shifted due to the angle changed, and when the infrared band pass filter is applied to the three-dimensional (3D) imaging system, the problem of unrecognizable or identification failure occurs when the light is received at a large angle.

SUMMARY

The present disclosure provides an infrared band pass filter, comprising: a first multilayer film, wherein the first multilayer film comprises: a plurality of Si:NH layers, wherein the refraction index of each Si:NH layer is larger than 3.5 in the wavelength range between about 800 nm and 1100 nm, and the extinction coefficient of the each Si:NH layer is smaller than 0.0002; and plurality of low refraction index layers a plurality of low refraction index layers, stacking with the plurality of Si:NH layers alternatively, wherein the refraction index of each low refraction index layer is smaller than 3 in the wavelength range between 800 nm and 1100 nm; wherein an difference value between the refraction index of the each Si:NH layer and the low refraction index layer is larger than 0.5.

According to one embodiment of the present disclosure, the infrared band pass filter further comprises a substrate; the first multilayer film is formed on one surface of the substrate.

According to one embodiment of the present disclosure, the infrared band pass filter further comprises a second multilayer film which is formed on the other surface of the substrate, being opposite to the first multilayer film.

According to one embodiment of the present disclosure, the second multilayer film comprises: a plurality of Si:NH layers, wherein the refraction index of each Si:NH layer is larger than 3.5 in the wavelength range between about 800 nm and 1100 nm, and the extinction coefficient of the each Si:NH layer is smaller than 0.0002; and plurality of low refraction index layers a plurality of low refraction index layers, stacking with the plurality of Si:NH layers alternatively, wherein the refraction index of each low refraction index layer is smaller than 3 in the wavelength range between 800 nm and 1100 nm; wherein an difference value between the refraction index of the each Si:NH layer and the low refraction index layer is larger than 0.5.

According to one embodiment of the present disclosure, the infrared band pass filter has a pass band partially overlapping with the wavelength range between 800 nm and 1100 nm, and the center wavelength of pass band is within the wavelength range between 800 nm and 1100 nm, and having a blocking level greater than OD5 in the wavelength range between 400 nm and 1100 nm.

According to one embodiment of the present disclosure, the infrared band pass filter has a pass band partially overlapping with the wavelength range between 800 nm and 1100 nm, and the center wavelength of the pass band is in the wavelength range between 800 nm and 1100 nm.

According to one embodiment of the present disclosure, when the incident angle is changed from 0 degrees to 30 degrees, and the center wavelength of the pass band is shifted less than 12 nm.

According to one embodiment of the present disclosure, the sum of the number of layers of the Si:NH layer and the number of layers of the low refraction index layer is less than 39 layers.

According to one embodiment of the present disclosure, the total thickness of the plurality of Si:NH layers and the plurality of low refraction index layers is less than 4.5 um.

According to one embodiment of the present disclosure, the hardness of infrared band pass filter is greater than Mohs hardness 7.

According to one embodiment of the present disclosure, the material of the low refraction index layer is selected from the group consisting of SiO₂, Al₂O₃, TiO₂, Nb₂O₅, Ta₂O₅, SiOH and SiNOH.

According to one embodiment of the present disclosure, the material of the low refraction index layer is SiO2, the refraction index of the low refraction index layer is between 1.4 and 1.5 in a wavelength range between 800 nm and 1100 nm.

According to the embodiment of the present disclosure, when the incident angle is changed from 0 degrees to 30 degrees, the center wavelength of the pass band is shifted less than 11.8 nm.

According to one embodiment of the present disclosure, the material of the low refraction index layer is SiNOH, the refraction index of the low refraction index layer is between 1.5 and 2 in a wavelength range between 800 nm and 1100 nm.

According to one embodiment of the present disclosure, when the incident angle is changed from 0 degrees to 30 degrees, the center wavelength of the pass band is shifted less than 11.1 nm.

According to one embodiment of the present disclosure, the hardness of infrared band pass filter is greater than Mohs hardness 9.

According to one embodiment of the present disclosure, the extinction coefficient of the Si:NH layer is less than 0.00012 in the wavelength range between 800 nm and 1100 nm.

According to one embodiment of the present disclosure, the transmissivity of pass band is greater than 90% in the wavelength between 800 nm and 1100 nm.

Compared with the prior art, the present disclosure can obtain the following technical effects:

The present disclosure provides an infrared band pass filter. The infrared band pass filter of the present disclosure is formed by alternatively stacking a Si:NH layer and a low refraction index layer, which has a pass band in a wavelength range between 800 nm and 1100 nm. When the incident angle is changed from 0 degrees to 30 degrees, the center wavelength of the pass band is shifted less than 12 nm, and the infrared band pass filter of the present disclosure can applied to the 3D imaging system to improve the 3D image analysis capability.

It should be understood, however, that this summary may not contain all aspects and embodiments of the present disclosure, that this summary is not meant to be limiting or restrictive in any manner, and that the disclosure as disclosed herein will be understood by one of ordinary skill in the art to encompass obvious improvements and modifications thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the exemplary embodiments believed to be novel and the elements and/or the steps characteristic of the exemplary embodiments are set forth with particularity in the appended claims. The Figures are for illustration purposes only and are not drawn to scale. The exemplary embodiments, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which:

FIG. 1 shows the schematic diagram of an infrared band pass filter according to a first embodiment of present disclosure;

FIG. 2 shows a curve graph of the transmission spectrum of the Si:NH layer according to the first embodiment of the present disclosure;

FIG. 3 shows curve graph of the transmission spectrum of incident angle from 0 degrees to 30 degrees of the infrared band pass filter;

FIG. 4 shows the infrared band pass filter according to a second embodiment;

FIG. 5 shows the curve graph of the transmission spectrum of incident angle from 0 degrees to 30 degrees of the first multilayer film according to the second embodiment;

FIG. 6 shows the curve graph of the transmission spectrum of incident angle from 0 degrees to 30 degrees of the second multilayer film according to the second embodiment; and

FIG. 7 shows the curve graph of the transmission spectrum of incident angle from 0 degrees to 30 degrees of the infrared band pass filter according to the second embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the disclosure are shown. This present disclosure may, however, be embodied in many different founts and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but function. In the following description and in the claims, the terms “include/including” and “comprise/comprising” are used in an open-ended fashion, and thus should be interpreted as “including but not limited to”. “Substantial/substantially” means, within an acceptable error range, the person skilled in the art may solve the technical problem in a certain error range to achieve the basic technical effect. The following description is of the best-contemplated mode of carrying out the disclosure. This description is made for the purpose of illustration of the general principles of the disclosure and should not be taken in a limiting sense. The scope of the disclosure is best determined by reference to the appended claims.

Moreover, the terms “include”, “contain”, and any variation thereof are intended to cover a non-exclusive inclusion. Therefore, a process, method, object, or device that includes a series of elements not only includes these elements, but also includes other elements not specified expressly, or may include inherent elements of the process, method, object, or device. If no more limitations are made, an element limited by “include a/an . . . ” does not exclude other same elements existing in the process, the method, the article, or the device which includes the element.

In the following embodiment, the same reference numerals is used to refer to the same or similar elements throughout the disclosure.

FIG. 1 shows the schematic diagram of an infrared band pass filter according to a first embodiment of present disclosure. As shown in FIG. 1, the embodiment provides an infrared band pass filter 1 adapted for a 3D imaging system. The infrared band pass filter 1 comprises a first multilayer film 11. The first multilayer film 11 comprises a plurality of Si:NH layers 111 and a plurality of low refraction index layers 112, and the plurality of low refraction index layers 112 are stacking with the plurality of Si:NH layers alternatively. The refraction index of each Si:NH layer 111 is larger than 3.5 in the wavelength range between 800 nm and 1100 nm, and the extinction coefficient of the each Si:NH layer is smaller than 0.0002. In another embodiment, the extinction coefficient of the each Si:NH layer less than 0.00012. The refraction index of each low refraction index layer 112 is smaller than 3 in the wavelength range between 800 nm and 1100 nm; wherein an difference value between the refraction index of the each Si:NH layer 111 and the low refraction index layer 112 is larger than 0.5.

In the embodiment, the sum of the number of Si:NH layers 111 and the number of low refraction index layer 112 is smaller than 39 layers. The total thickness of the plurality of Si:NH layers 111 and the plurality of low refraction index layers 112 is smaller than 4.5 um. In the embodiment, the infrared band pass filter 1 has some band pass overlapping the wavelength range between 800 nm and 1100 nm. The center wavelength of the band pass is located in the wavelength range between 800 nm and 1100 nm.

While the incidence angle is changed from 0 degrees to 30 degrees, the center wavelength of the pass band is shifted less than 12 nm. Transmissivity of the band pass is larger 90% in the wavelength range between 800 nm and 1100 nm. In the embodiment, the hardness of the infrared band pass filter is larger than Mohs' hardness 7. In the embodiment, the center wavelength of the big angle of the infrared band pass filter 1 being smaller can solve the 3D imaging analyze problem effectively, while the thickness of the infrared band pass filter 1 of the present embodiment is slimmer than the infrared band pass filter of the prior technology so as to decrease the warping phenomenon of the infrared band pass filter 1.

In the embodiment, manufacture method of the infrared band pass filter 1 is to form the Si:NH layer 111 and the low refraction index layer 112 by the sputter deposition. The process of the sputter deposition is that the mid frequency sputter power source output 50 KHz voltage through the inside electrical network, respectively applied on a pair of silicon target on the sputtering machine. Argon is inputted into the silicon target via the air duct so as to generate light and discharge and generate the steady plasma.

Due to the reaction chamber of the sputtering machine has the quadrature field being vertical to the electrical filed, the movement direction of the electron is changed and limited in the certain space so as to increase the collision probability with the argon and ionization effect of electron.

The argon ion elected from ionization effect crash the silicon target quickly in the electrical field, and the mass silicon atom is sputtered out, while inductively coupled plasma (ICP) is mixed with ammonia to generate the Si:NH layer 111 which has the refraction index larger than 3.5 in the wavelength range between 800 nm and 1100 nm. The low refraction index layer 112 is selected from the group consisting of SiO₂.SiOH or SiNOH, and the ICP is mixed with oxygen/ammonia to generate the low refraction index layer which the refraction index is smaller than 3 in the wavelength range between 800 nm and 1000 nm. If the low refraction index layer 112 is Al₂O₃.TiO₂.Nb₂O₅ or Ta₂O₅, the silicon target of the sputtering machine is replaced with an aluminum target, a titanium target, a tantalum target or a tantalum target, and formed by the above method.

TABLE 1 TG4 gas ICP gas At 940 nm At 940 nm Material Argon Argon oxygen Ammonia n (Opt) k (Opt) SiNOH 60 500 5 30 3.42022 8.35E−05 SiNOH 60 500 10 30 3.267666 6.24E−05 SiNOH 60 500 30 30 2.781278 3.23E−05 SiNOH 60 500 70 30 2.176382 2.27E−04 SiNOH 60 500 76 30 2.125067 2.60E−04 SiNOH 60 500 80 30 2.037629 1.85E−04 SiNOH 60 500 88 30 1.986488 1.94E−04 SiNOH 60 500 95 30 1.908388 1.42E−04 SiNOH 60 500 104 30 1.846262 1.69E−04 SiNOH 60 500 125 30 1.576734 1.26E−05

As shown in Table 1, the refraction index of the low refraction layer 112 of the embodiment will changed along with the change of the oxygen flow via the spurting process in the wavelength 940 nm. When the oxygen flow is becoming bigger, then the refraction index of the low refraction index layer 112 in the wavelength 940 nm is becoming lower. When the low refraction index layer 112 is SiNOH, the refraction index of the low refraction index layer 112 is between 1.5 and 2 in the wavelength range between 800 nm and 1100 nm. When the low refraction index layer 112 is SiO₂, the refraction index of the low refraction index layer 112 is between 1.4 and 1.5 in the wavelength range between 800 nm and 1100 nm.

FIG. 2 shows a curve graph of the transmission spectrum of the Si:NH layer according to the first embodiment of the present disclosure. As shown in FIG. 2, the curve 21 is the transmission spectrum of the Si:NH layer and the curve 22 is the transmission spectrum of the Ti₃O₅ layer. The absorption effect of the Si:NH layer 111 is better than the Ti₃O₅ layer used by the infrared band pass filter in the wavelength range between 350 nm and 700 nm. The infrared band pass filter 1 having Si:NH layer is applied in the 3D image system so as to increase the image analyze function of the 3D image system.

The material of the low refraction index layer 112 is selected from the group consisting of SiO₂.Al₂O₃.TiO₂.Nb₂O₅.Ta₂O₅.SiOH and SiNOH. The material of the low refraction index layer 112 is SiO₂, the refraction index of the low refraction index layer 112 is between 1.4 and 1.5 in the wavelength range between 800 nm and 1100 nm. The sum of the number of Si:NH layers 111 and the number of low refraction index layer 112 is 39 layers. The sum of thickness of the plurality of Si:NH layers 111 and the plurality of low refraction index layers 112 is 4.4 um. Table 2 shows the thickness list of each Si:NH layer 111 and each low refraction index layer 112.

TABLE 2 Number of layers material thickness (nm) 1 SiO₂ 82.19 2 Si:NH 253.51 3 SiO₂ 118.19 4 Si:NH 41.54 5 SiO₂ 306.22 6 Si:NH 92.21 7 SiO₂ 78.43 8 Si:NH 69.85 9 SiO₂ 70.53 10 Si:NH 57.16 11 SiO₂ 280.38 12 Si:NH 233.19 13 SiO₂ 103.92 14 Si:NH 21.84 15 SiO₂ 124.75 16 Si:NH 99.93 17 SiO₂ 99.75 18 Si:NH 41.78 19 SiO₂ 295.9 20 Si:NH 61.93 21 SiO₂ 108.78 22 Si:NH 31.22 23 SiO₂ 106.84 24 Si:NH 82.33 25 SiO₂ 128.68 26 Si:NH 132.25 27 SiO₂ 121.07 28 Si:NH 80.92 29 SiO₂ 300.84 30 Si:NH 94.95 31 SiO₂ 102.9 32 Si:NH 49.42 33 SiO₂ 113.78 34 Si:NH 15.21 35 SiO₂ 288.75 36 Si:NH 4.87 37 SiO₂ 89.27 38 Si:NH 17.57 39 SiO₂ 15.54

FIG. 3 shows curve graph of the transmission spectrum of incident angle from 0 degrees to 30 degrees of the infrared band pass filter. As shown in FIG. 3, it shows the transmission spectrum curve 31 in the incident angle of 0 degrees and the transmission spectrum curve 32 in the incident angle of 30 degrees. The center wavelength of the band pass is 946 nm in the incident angle of 0 degrees in the embodiment. The center wavelength of the band pass is 934.2 nm in the incident angle of 30 degrees in the embodiment. Therefore, when the incident angle of the infrared band pass filter is changed from 0 degrees to 30 degrees, the offset amplitude of the center wavelength of the band pass is smaller than 11.8 nm. The transmissivity of the band pass is larger than 90% in the wavelength range between 800 nm and 1100 nm.

FIG. 4 shows the infrared band pass filter according to a second embodiment. As shown in FIG. 4, the infrared band pass filter 1 comprises a first multilayer film 11 a, a second multilayer film 11 b and an optical substrate 12. The first multilayer film 11 a and the second multilayer film 11 b are respectively arranged the two opposite surfaces 121 of the optical substrate 12. Specifically, the first multilayer film 11 a and the second multilayer film 11 b respectively has a structure of the plurality of Si:NH layers 111 alternatively stacking with the plurality of low refraction index layers 112. The manufacture methods of the Si:NH layer 111 and the low refraction index layer 112 are described above. In the embodiment, the thickness of the infrared band pass filter is slimmer than the infrared band pass filter of the prior technology, and while the infrared band pass filter 1 of the embodiment has two multilayer films, the two multilayer films will be maintained balance via film stress so as to decrease the warp phoneme happen of the infrared band pass filter.

In the infrared band pass filter 1 of the embodiment, the material of the low refraction index layer 112 of the first multilayer film 11 a is SiNOH. The sum of the number of the Si:NH layer 111 and the number of the low refraction index layer 112 is 39 layers. The total thickness of the plurality of Si:NH layer 111 and the plurality of low refraction index layer 112 is 4.3 um. Table 3 shows the thickness list of the each Si:NH layer 111 and each low refraction index layer 112.

TABLE 3 Number of layers Material Thickness (nm) 1 SiNOH 297 2 Si:NH 15.1 3 SiNOH 38.88 4 Si:NH 115.6 5 SiNOH 211.44 6 Si:NH 280.91 7 SiNOH 62.06 8 Si:NH 79.67 9 SiNOH 50.49 10 Si:NH 70.88 11 SiNOH 81.85 12 Si:NH 306.07 13 SiNOH 19.97 14 Si:NH 104 15 SiNOH 103.41 16 Si:NH 124.59 17 SiNOH 38.43 18 Si:NH 99.3 19 SiNOH 55.11 20 Si:NH 295.27 21 SiNOH 28.61 22 Si:NH 108.38 23 SiNOH 74.2 24 Si:NH 105.09 25 SiNOH 114.44 26 Si:NH 127.7 27 SiNOH 69.68 28 Si:NH 121.36 29 SiNOH 6.85 30 Si:NH 288.78 31 SiNOH 44.21 32 Si:NH 102.59 33 SiNOH 14.23 34 Si:NH 112.35 35 SiNOH 83.11 36 Si:NH 299.68 37 SiNOH 14.19 38 Si:NH 89.14 39 SiNOH 80.45

Please refer to FIG. 5, which shows the curve graph of the transmission spectrum of incident angle from 0 degrees to 30 degrees of the first multilayer film according to the second embodiment of the present disclosure; as shown in FIG. 5, which shows the transmission spectrum curve 41 at the incident angle 0 degrees and the transmission spectrum curve 42 at the incident angle 30 degrees. In the present embodiment, the center wavelength of band pass is in 939.9 nm at an incident angle of 0 degrees and the center wavelength is in 932.8 nm at an incident angle of 30 degrees. Therefore, when the infrared band pass filter of the present embodiment is changed from 0 degrees to 30 degrees, the center wavelength of the pass band is shifted less than 11.1 nm. The transmission of the pass band in the wavelength range between 800 nm and 1100 nm is more than 90%.

However, the material of the low refraction index layer 112 of the second multilayer film 11 b of the present embodiment also uses SiNOH, and the total number of layers of the Si:NH layer 111 and the low refraction index layer 112 is 32 layers. The total thickness of the plurality of Si:NH layers 111 and a plurality of low refraction index layers 112 of the second multilayer film 11 b is 2.7 um. The Table 3 below lists the thicknesses of each Si:NH layer 111 and the low refraction index layer 112.

TABLE 3 Number of layers Material Thickness (nm) 1 SINOH 20.84 2 SINH 85.77 3 SINOH 121.13 4 SINH 72.85 5 SINOH 128.99 6 SINH 138 7 SINOH 108.69 8 SINH 49.76 9 SINOH 150.76 10 SINH 110.88 11 SINOH 47.85 12 SINH 121.71 13 SINOH 145.74 14 SINH 127.98 15 SINOH 63.26 16 SINH 122.03 17 SINOH 31.33 18 SINH 91.1 19 SINOH 46.32 20 SINH 101.34 21 SINOH 53.27 22 SINH 99.56 23 SINOH 57.74 24 SINH 71.18 25 SINOH 45.12 26 SINH 96.14 27 SINOH 52.1 28 SINH 91.74 29 SINOH 56.67 30 SINH 73.42 31 SINOH 19.03 32 SINH 72.95

Referring to FIG. 6 and FIG. 7 again, it shows the curve graph of the transmission spectrum of the second multilayer film of the second embodiment of the present disclosure at an incident angle of 0 degrees and 30 degrees, and the curve graph of the transmission spectrum of the infrared band pass filter of the second embodiment of the present disclosure at an incident angle of 0 degrees and 30 degrees. As shown in FIG. 6, the transmission spectrum curve 51 at the incident angle 0 degrees and the transmission spectrum curve 52 at the incidence angle 30 degrees. The second multilayer film 11 b of the present embodiment is used to increases the transmissivity of the infrared band pass filter. As can be seen from FIG. 6, the transmissivity of the pass band of the infrared band pass filter in the wavelength range between 800 nm and 1100 nm is greater than 90%, meanwhile, the outside of the pass band of the infrared band pass filter has a blocking level which is larger than OD5 in the wavelength range between 400 nm and 1100 nm. FIG. 7 shows the transmission spectrum curve 61 at an incident angle 0 degrees and the transmission spectrum curve 62 at an incident angle 30 degrees. The infrared band pass filter of the present embodiment, at an incident angle 0 degrees, has the center wavelength of the pass band being at 943.9 nm. The infrared band pass filter of this embodiment, at an incident angle 30 degrees, the center wavelength of pass band being at 932.8 nm. Therefore, when the infrared band pass filter of the present embodiment is changed from 0 degrees to 30 degrees, the shift wavelength of the center wavelength of the pass band is less than 11.1 nm.

The Mohs hardness of the infrared band pass filter of the embodiment can achieve to 9 and 9.5. The Vickers hardness is about 2200, and the micro-hardness is 32630 MPa, thus demonstrating that the infrared band pass filter of the embodiment has good chemical resistance, and having a good chemical corrosion resistance under inorganic acid, less than 30% caustic soda solution or organic acid, also being a high performance electrical insulation material. The material of the low refraction index layer 112 of the first multilayer film 11 a and the second multilayer film 11 b of the present embodiment can also be made of other materials such as SiO₂.Al₂O₃.Ti O₂.Nb₂O₅.Ta₂O₅ or SiOH. The stacked of the Si:NH layer 111 and the low refraction index layer 112 of the first multilayer film 11 a and the stacked of the Si:NH layer 111 and the low refraction index layer 112 of the second multilayer film 11 b of the present embodiment are mutually change.

In summary, in one or more embodiments of the present disclosure, the present disclosure provides an infrared band pass filter, which having at least one multilayer film. The multilayer film is formed by the Si:NH layer and the low refraction index layer alternatively stacked, which having a pass band in a wavelength range between 800 nm and 1100 nm. When the incident angle is changed from 0 degrees to 30 degrees, the center wavelength of the pass band is shifted by less than 12 nm. The shift of the large-angle center wavelength of the infrared band pass filter of the present disclosure is small, and the infrared band pass filter of the present disclosure can improve the three-dimensional image resolution capability when applied to a three-dimensional imaging system.

It is to be understood that the term “comprises”, “comprising”, or any other variants thereof, is intended to encompass a non-exclusive inclusion, such that a process, method, article, or device of a series of elements not only includes those elements but also includes other elements that are not explicitly listed, or elements that are inherent to such a process, method, article, or device. An element defined by the phrase “comprising a . . . ” does not exclude the presence of the same element in the process, method, article, or device that comprises the element.

Although the present disclosure has been explained in relation to its preferred embodiment, it does not intend to limit the present disclosure. It will be apparent to those skilled in the art having regard to this present disclosure that other modifications of the exemplary embodiments beyond those embodiments specifically described here may be made without departing from the spirit of the disclosure. Accordingly, such modifications are considered within the scope of the disclosure as limited solely by the appended claims. 

What is claimed is:
 1. An infrared band pass filter, comprising: a first multilayer film, wherein the multilayer film comprises: a plurality of Si:NH layers, wherein an refraction index of each Si:NH layer is larger than 3.5 in an wavelength range between about 800 nm and 1100 nm, and the extinction coefficient of the each Si:NH layer is smaller than 0.0002; and a plurality of low refraction index layers, stacking with the plurality of Si:NH layers alternatively, wherein the refraction index of each low refraction index layer is smaller than 3 in the wavelength range between 800 nm and 1100 nm; wherein an difference value between the refraction index of the each Si:NH layer and the low refraction index layer is larger than 0.5.
 2. The infrared band pass filter of claim 1, further comprising a substrate, wherein the substrate is mounted in the first multilayer film.
 3. The infrared band pass filter of claim 2, further comprising: a second multilayer film, formed on the other surface of the substrate, opposite to the first multilayer film.
 4. The infrared band pass filter of claim 3, wherein the second multilayer film comprises: a plurality of Si:NH layers, wherein the refraction index of each Si:NH layer is larger than 3.5 in the wavelength range between about 800 nm and 1100 nm, and the extinction coefficient of the each Si:NH layer is smaller than 0.0002; and a plurality of low refraction index layers, stacking with the plurality of Si:NH layers alternatively, wherein the refraction index of each low refraction index layer is smaller than 3 in the wavelength range between 800 nm and 1100 nm; wherein an difference value between the refraction index of the each Si:NH layer and the low refraction index layer is larger than 0.5.
 5. The infrared band pass filter of claim 3, wherein the infrared band pass filter has a pass band partially overlapping with the wavelength range between 800 nm and 1100 nm, and the center wavelength of pass band is within the wavelength range between 800 nm and 1100 nm, and having a blocking level greater than OD5 in the wavelength range between 400 nm and 1100 nm.
 6. The infrared band pass filter of claim 1, wherein the infrared band pass filter has a pass band partially overlapping with the wavelength range between 800 nm and 1100 nm, and the center wavelength of the pass band is in the wavelength range between 800 nm and 1100 nm.
 7. The infrared band pass filter of claim 6, wherein when the incident angle is changed from 0 degrees to 30 degrees, the center wavelength of the pass band is shifted less than 12 nm.
 8. The infrared band pass filter of claim 1, wherein the sum of the number of layers of the Si:NH layer and the number of layers of the low refraction index layer is less than 39 layers.
 9. The infrared band pass filter of claim 1, wherein the total thickness of the plurality of Si:NH layers and the plurality of low refraction index layers is less than 4.5 um
 10. The infrared band pass filter of claim 1, wherein the hardness of infrared band pass filter is greater than Mohs hardness
 7. 11. The infrared band pass filter of claim 6, wherein the material of the low refraction index layer is selected from the group consisting of SiO₂, Al₂O₃, TiO₂, Nb₂O₅, Ta₂O₅, SiOH and SiNOH.
 12. The infrared band pass filter of claim 11, wherein the material of the low refraction index layer is SiO₂, the refraction index of the low refraction index layer is between 1.4 and 1.5 in a wavelength range between 800 nm and 1100 nm.
 13. The infrared band pass filter of claim 12, wherein when the incident angle is changed from 0 degrees to 30 degrees; the center wavelength of the pass band is shifted less than 11.8 nm.
 14. The infrared band pass filter of claim 11, wherein the material of the low refraction index layer is SiNOH; the refraction index of the low refraction index layer is between 1.5 and 2 in a wavelength range between 800 nm and 1100 nm.
 15. The infrared band pass filter of claim 14, wherein when the incident angle is changed from 0 degrees to 30 degrees; the center wavelength of the pass band is shifted less than 11.1 nm.
 16. The infrared band pass filter of claim 14, wherein the hardness of infrared band pass filter is greater than Mohs hardness
 9. 17. The infrared band pass filter of claim 1, wherein the extinction coefficient of the Si:NH layer is less than 0.00012 in the wavelength range between 800 nm and 1100 nm.
 18. The infrared band pass filter of claim 6, wherein the transmissivity of pass band is greater than 90% in the wavelength between 800 nm and 1100 nm. 